In manufacturing, for example, a semiconductor part or a flat panel display, a substrate liquid processing apparatus has been used for performing an etching processing on a substrate such as, for example, a semiconductor wafer or a liquid crystal substrate with an etching liquid (a processing liquid).
A conventional substrate liquid processing apparatus includes a processing liquid storage unit that stores a processing liquid for processing a substrate, a processing liquid supply unit that supplies the processing liquid to the processing liquid storage unit, and a processing liquid circulation unit that circulates the processing liquid stored in the processing liquid storage unit to perform, for example, heating of the processing liquid.
In the substrate liquid processing apparatus, a plurality of substrates are immersed in the processing liquid stored in the processing liquid storage unit, so that the substrates are subjected to a liquid processing with the processing liquid. Further, in the substrate liquid processing apparatus, the processing liquid supplied from the processing liquid supply unit is circulated in the processing liquid circulation unit and heated to a predetermined temperature.
In the substrate liquid processing apparatus, when the substrates are repeatedly processed with the processing liquid, the concentration of, for example, impurities, which are contained in the processing liquid by the processing of the substrates, increases. Thus, the substrates may not be satisfactorily processed. For example, when the substrates are subjected to an etching processing with an aqueous phosphoric acid solution (an etching liquid), the capability (etching rate) of the processing liquid depends on the silicon concentration in the processing liquid. Thus, the silicon concentration in the processing liquid needs to be maintained in a predetermined range. However, the repetition of the processing of the substrates increases the silicon concentration in the etching liquid and decreases the capability of the processing liquid. Thus, the substrates may not be satisfactorily etched (see, e.g., Japanese Patent Laid-Open Publication No. 2001-23952).
Accordingly, in the conventional substrate liquid processing apparatus, a concentration sensor is provided in the processing liquid storage unit or the processing liquid circulation unit to measure the silicon concentration in the processing liquid.